Meet your body's best defense against weight gain: lean muscle

This Way to a Tight Toned Body

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How would you like to magically burn off about 40 calories in the next 15 minutes, without even breaking a sweat? Want to try? Okay, here's what you do:

Go into the bedroom. Open up the closet. Look inside. Anything need to go to the dry cleaner? What about that pashmina you spilled New Year's bubbly on? Toss it in the laundry bag. Straighten a few hanging items and refold your sweaters so the inside of your wardrobe doesn't look like you had to flee the paparazzi. Good job. Now have a seat.

Ta-da! You've just smoked 40 or more calories in less time than it takes to put on your makeup, and all you did was neaten up your clothes. Magic, right?

Well, not really. You see, your body is already primed to be a fat-burning machine. All you need to do to start changing your body's shape is tune up that fat furnace and get it revving at maximum efficiency so you're burning even more fat while going about the mundane rituals of life.

This fat-burning magic comes from your metabolism, a word you've probably heard tossed around a lot but maybe don't quite understand. What is metabolism? Simply put, it's all the various chemical reactions that happen inside your body, 24-7, that keep you alive. It's food being turned into energy and that energy being burned off to keep your hair growing, your heart beating, your liver pumping out bile, your lungs transferring oxygen into your bloodstream, and your intestines turning Amstel Light into urine (not that there's a huge leap there). It's the engine room of your individual starship, your never-ending calorie burn. And while you may imagine that the majority of your calories get burned while you're engaged in some strenuous activity like riding a bike, diving into a pool, or getting jiggy with your honey, you're actually burning most of your calories, well, just keeping the lights on.

In fact, think of metabolism as your caloric 401(k) program. It's not going to give you instant gratification, like hitting a slot machine jackpot. It's a long-term strategy, but it's a sure thing: Invest in it and you'll get slow, steady, effective returns that will keep you happy and healthy for years to come. (But if you want to lose weight even faster, you're going to have to overhaul your eating habits. Find out how with The Women's Health Diet.)

Now, like any long-term investment, it needs a little maintenance from time to time. We'll show you the smart ways to tweak your metabolism, improving your burn just enough to gain even more over the long haul. (Or to borrow what they say in financial circles, it's time to work less for your calorie burn and have your calorie burn start working for you!) Prepare for a few surprises, starting with...